Azelaic acid

Azelaic acid

Therapv I I Ill Azelaic acid Marcella Nazzaro-Porro, M.D. Rome, Italy This review is an update on the literature accumulated over the past 10 years...

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Therapv I

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Ill

Azelaic acid Marcella Nazzaro-Porro, M.D. Rome, Italy This review is an update on the literature accumulated over the past 10 years following the original observation that azelaic acid, a naturally occurring and nontoxic C9 dicarboxylic acid, possesses significant biologic properties and a potential as a therapeutic agent. These studies have shown that azelaic acid is a reversible inhibitor of tyrosinase and other oxidoreductases in vitro and that it inhibits mitochondrial respiration. It can also inhibit anaerobic glycolysis. Both in vitro and in vivo it has an antimicrobial effect on both aerobic and anaerobic (PropionibacteHum aches) microorganisms. In tissue culture it exerts a dose- and time-dependent cytotoxic effect on malignant melanocytes, associated with mitochondrial damage and inhibition of deoxyribonucleic acid (DNA) synthesis. Tumoral cell lines not containing tyrosinase are equally affected. Normal cells in culture exposed to the same concentrations of the diacid that are toxic for tumoral cells are in general not damaged. Radioactive azelaic acid has been shown to penetrate tumoral cells at a higher level than normal cells of the corresponding line. Topically applied (a 20% cream), it has been shown to be of therapeutic value in skin disorders of different etiologies. Its beneficial effect on various forms of acne (comedogenic, papulopustular, nodulocystic) has been clearly demonstrated. Particularly important is its action on abnormal melanocytes, which has led to the possibility of obtaining good results on melasma and highly durable therapeutic responses on lentigo maligna. It is also capable of causing regression of cutaneous malignant melanoma, but its role in melanoma therapy remains to be investigated. From the correlation of laboratory results with the in vivo observations, it can be suggested that the mode of action of azelaic acid is related to its higher penetrability of abnormal cells compared with normal cells and to its capability of reversibly inhibiting essential enzymatic activities. (J AM ACAD DERMATOLI987;17:1033-41.)

A z e l a i c acid is a saturated 9 carbon atom dicarboxylic acid (COOH-(CH2)7-COOH) that owes its n a m e to the fact that it was originally obtained f r o m the oxidation of oleic acid by nitric acid ( A Z = azote = nitrogen;, elaion = oil). It is w e l l k n o w n in industry, where it is used for the formation o f polymeric materials, and it can be

From Istituto Dermatologico Sat~ Gallican0. Supported by grants from CNR, Italy, Project "Ontology" No. 85.02270.44, the Cancer Research Campaign, the Wellcome Trust, and by grants from Schering AG, Berlin. Reprint requests to: Dr. Marcella Nazzaro-Porro, Istituto Dermatologico San Fallicano, via San Gallicano 25/A, 00153 Rome, Italy.

obtained, apart from the oxidation of fatty acids unsaturated in position 9, by fermentation by a variety o f microorganisms, for example, Brettanomyces petrophilum.* In man it is found, along with other dicarboxylic acids, in the urine of patients with noncompensated diabetes, and of individuals with a congenital or acquired inabiIity to oxidize monocarboxylic acids, i Our interest in azelaic acid derived initially from studies on pityriasis versicolor, a common skin *Mitsabishi Petrochemical Co., Ltd., Japan. Microbial production of long chain dicarboxylic acids. Jpn Kokkai Tokkio Koho JP 57/7889, May 19, 1982.

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disease caused by the fungus Pityrosporum that, as was recently dem0nstrated, z possesses lipoxygenases that acton different unsaturated fats present in skin surface lipids. In culture, the fungus is capable Of oxidizing oleic acid to azelaic acid, 3 and when it was demonstrated that azelaic acid is a competitive inhibitor of tyrosinase, ~ the key enzyme for melanogenesis, it seemed possible that it could be involved in the hypochromia of pityriasis versicolorl Since it was well known that some phenolic compounds that act as alternative substrates for tyrosinase have depigmenting properties w h e n applied topically on the skin, 4 it was thought that azelaic acid might have a similar effect. It soon became evident that the diacid had no depigmenting activity upon normal skin, nor had it any toxic effect. The achromia in pityriasis versicolor, therefore, cannot be due to azelaic acid. As suggested by subsequent studies, it is more likely due to toxic lipoperoxides formed by the action of Pityrosporum on the unsaturated lipids of the Skin surface. 2 However, azelaic acid had a positive therapeutic action on melanosis because of hyperfunctioning Or proliferative melanocytes, as in melasma5 or lentigo maligna. 6 Some patients being treated for melasma coincidentally reported a beneficial effect on their acne. 7 Thus there emerged a peculiar characteristic of azelaic acid: without being in any w~.y toxic for normal skin, it could exert a beneficial therapeutic action on skin disorders of different etiology. The studies carried out over the past 10 years have been largely aimed at elucidating the mechanism of action of azelaic acid and investigating its therapeutic value. PHARMACOKINETICS AND TOXICITY In healthy humans, approximately 60% of the amount of azelaic acid orally administered, inde: pendent of the dosage, is excreted unchanged in the Urine within 12 hours of ingestion. Besides azelaic acid (C9 dicarboxylic acid), the C7 and C5 dicarboxylic acids have been found in the urine, demonstrating the [3.-oxidation pathway of biotransformation of azelaic acid in humans. The excretion of unchanged azelaic acid is completed within 12 hours. Concentrations of azelaic acid in human serum peak between 2 and 3 hours after

administration. After 8 hours the serum levels are negligible. No azelaic acid is found in the feces 8 The fate of azelaic acid nonrecovered in the urine was studied in rats following administration of 1,9-J4C azelaic acid. ~4C was found in lipid extracts of different tissues, mainly in the fatty acid portion of triglycefides and phospholipids, confirming the [3-oxidation of azelaic acid to malonyl CoA, which enters the biosynthesis of fatty acids. ~4C (14.5%) was also recovered from expired air? Investigations after oral administration of azelaic acid in rats and rabbits showed the absence of acute toxicity (no LD.~0 was found up to 4000 mg/kg). No significant differences in biologic parameters (blood chemistry values, hematologic values, serum proteins, growth curves, and histologic findings of the different organs) were observed in animals during the period of treatment (180 days, 280 and 400 mg/kg/day for rats and rabbits, respectively), compared with control animals. Azelaic acid was in no way harmful for newborn animals even when administered in high dosage during pregnancy and suckling periods. The development of the fetuses was normal.* In humans, azelaic acid has been administered topically or systemically without deleterious effect. 9 MECHANISMS OF ACTION

Experimental findings in vitro Antienzymatic and antimitochondrial activity. In addition to being a competitive inhibitor of tyrosinase, ~ azelaic acid is a reversible inhibitor of the activity of cytochrome P450 reductasel" and 5 c~-reductase in microsomal preparations supplemented with reduced nicotinamide adenine dinucleotide phosphate (NADPH). ~° In addition, azelaic acid can reversibly inhibit some enzymes of the respiratory chain (reduced nicotinamide ade*Mingmne G, Greco AV, Nazzaro-Porro M, Passl S. Toxicity of azelaic acid. Drugs Exp Clin Res 1983;9:447-55. "l'Nazzaro-Porro M, Confaloni AM, Serlupi-Crescenzi G, Picardo M, et ai. Effect of medium chain length dicarboxylic acids on microsomal mixed function oxidases. Proceedings of Vlth European Workshop on Melanin Pigmentation, Murcia, Spain, March 22, 1985.

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nine dinucleotide [NADH]-dehydrogenase, succinic acid dehydrogenase, reduced ubiquinone cytochrome c oxidoreductase). 11 In isolated rat liver mitochondria the formation of adenosine triphosphate is reduced proportionally to the concentration of azelaic acid in the medium, n Of particular interest is the fact that the diacid, apart from its action on aerobic respiration, has an inhibitory effect also on anaerobic glycolysis. In fact, a significant reduction in lactate formation was observed w h e n a crude extract of chicken embryo was preincubated for 60 minutes with azelaic acid. At the s a m e conditions, purified yeast hexokinase was also significantly inhibited. 12 A n t i m i c r o b i a l and antiviral effect. The antimicrobial effect of azelaic acid has been demonstrated in culture against aerobic microorganisms (Staphylococcus aureus, Proteus mirabilis, Escherichia coli, Pseudomonas aeruginosa, Candida albicans) and the anaerobic Propionibacterium acnes. 10.13-15An inhibitory effect on vaccinia virus replication has also been shown.* Effects on tumoral and normal cells in cul. ture. In cultures of melanoma cells~6z3't and of l y m p h o m a and leukemia-derived cell lines, lsa4 azelaic acid has been shown to have a dose- and time-dependent inhibitory effect on both proliferation and viability. With melanoma cells in culture, it has been shown to have an inhibitory effect on D N A synthesis is and on plasminogen activator activity. 2° Ultrastructurally, swelling and damage to mitochondria, without visible deleterious effect on other cytoplasmic membranous organelles, and accumulation of lipid droplets are characteristic features o f malignant melanocytes exposed to azelaic acid in culture, z2.25 The addition of carnitine to the m e d i u m significantly increases mitochondrial swelling, 26 suggesting an enhanced transport of azelaic acid across the mitochondrial mere-

*Reith RW, Williamson JD, Breathnach AS, Robins EJ, NazzaroPorro M. Inhibition of vaccinia virus replication by azelaic acid. IRCS Med Sei 1985;13:783-4. tSchachtschabel DO, Inhibition of cell proliferation of cultured melanoma cells by azelaic acid and other long chain dicarboxylic acids. Proceedings of Vth European Workshop on Melanin Pigmentation, Marseille, France, Sept. 10, 1984.

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branes. Ultrastructural autoradiography 2v confirmed penetration of dicarboxylic acids into mitochondria, which are sites of B-oxidation. It is important to note that in all of the above in vitro experiments, whether enzymologic, microbiologic, or on tumoral cell cultures, the inhibitory activity of azelaic acid became evident only when the diacid was present in the medium at high concentration (10 -3 M) and increased with the dosage. Of particular interest is the fact that, by using the same incubation times and the same concentrations of the diacid that are toxic for tumoral cells, normal cells in culture, such as monkey melanocytes,22 human lymphocytes ,24human and mufine fibroblasts, 2a'24 and keratinocytes TM are in general not affected. Some ultrastructural damage, however, has been observed in pure cultures of normal human melanocytes, 25 and a reversible antiproliferative effect has been noted in cultures of neonatal mouse keratinocytes. 28 It is possible that these effects of azelaic acid are correlated with the turnover rate of the cells in these instances. In fact, in the first case the melanocytes are stimulated to proliferate and duplicate by the presence in the medium o f cholera-toxin and 12-0-tetradecanoyt phorbol-I 3-acetate; in the case of neonatal cells, their rate of duplication is probably higher than that of ceils obtained from adult animals. The above laboratory results are in general in line with the in vivo observations. A cream containing a high concentration of azelaic acid (20% = --1 M) has no deleterious effect on normal skin, 6 while it is therapeutically active on cutaneous disorders of different etiology, A possible explanation for this difference of effect between normal and abnormal cells both in vitro and in vivo is provided by the results of experiments with radioactive azelaic acid, It was shown to penetrate tumoral ceils at two to three times higher level than normal cells of the corresponding lines,Z4 and the degree of toxicity for the tumoral cells was proportional to the uptake of the diacid. 24 Both normal and tumoral cells metabolize dicarboxylic acids by [3-oxidation2a.z7; the greater permeability of tumoral ceils, compared with normal cells, could lead to an excess of the diacid beyond their

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capability to metabolize it fully, and this excess in their case could exert a toxic effect probably by inhibiting enzymatic activities essential for the cell. It could further be suggested, if permeability is indeed a factor, that the higher uptake could be related to the functional state of the cell, and this could explain an effect of the diacid also on abnormally active but not tumoral cells such as the melanocytes in melasma.

Experimental findings in vivo Let us consider reported positive therapeutic effects of topically applied azelaic acid. It is effective in melanosis because of hyperfunction or proliferation of melanocytes (melasma, 5 lentigo maligna, 6'~8) and is capable of causing regression of lesions o f primary cutaneous malignant melanoma. 29 It has a beneficial effect on different forms o f ache vulgaris, 7'3° and pilot studies from our Institute (unpublished) also indicate a beneficial ~ffect on seborrheic dermatitis and, in particular, on rosacea. In this last condition, a positive response was obtained not only with the acneiform lesions but also with the vascular component (erythema and telangiectasia) and, when present, with seborrhea, In addition, there are individual reports of some success with solar keratosis and Bowen's disease. The preceding conditions, although from different causes, all respond positively to azelaic acid. This raises the question of its mode of action. Does azelaic acid operate by interfering with a variety o f unrelated etiopathogenetic factors, or via a more general mechanism o f action? It is not possible at present to give a definite answer to this question, but by correlating the effects in vivo with laboratory results, some pointers may emerge. Pigmentary disorders. Ultrastructural studies on the effect of azelaic acid on lentigo maligna 6 and on selected cases o f cutaneous malignant melanoma 29 have shown morphoIogic features analogous with those observed in melanoma cells exposed to high concentration of azelaic acid in culture, 22,25 that is, swelling and degeneration of mitochondria accompanied by accumulation of lipid droplets in the cytoplasm, leading to cell death. Adjacent keratinocytes, by contrast, ap-

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peared structurally normal. Accepting greater penetrability of the malignant melanocytes, and bearing in mind current theories that mitochondria represent "weak points" of tumoral cells, a~ one can suggest, in agreement with the in vitro studies," that one of the more significant activities of azelaic acid involves a progressive inhibition of cellular respiration. The reduction in energy supply could be contributed to by a reduction of anaerobic glycolysis ~2 and accompanied by inhibition of DNA synthesis, j8 Considering the overall studies reported above, it is clear that the antityrosinase effect per se is not essential for the cytotoxicity of azelaic acid; however, one cannot exclude the possibility that the inhibitory effect on tyrosinase activity might render the abnormal melanocytes more sensitive to the action of the diacid. Aene. Three principal factors are concerned with the etiopathogenesis of acne: the action of cutaneous microflora, especially P. a c h e s , keratinization of the pflosebaceous duct, and increased sebaceous secretion under the influence of androgen hormones. The antimicrobial effect of azelaic acid observed in vitro for aerobic microorganisms and the anaerobic P. a c n e s ~°,~3~5 has been recently confirmed in vivo in 45 patients with acne?° Regarding the second factor, a significant reduction in the size of tetradecanoate-induced comedones of the rabbit ear following treatment with topical azelaic acid has been reported. J5 A reduction in proliferation of neonatal mouse keratinocytes in culture has also been observed, as Conflicting results have been reported with experiments on the effect of the diacid on sebogenesis in vitro. ~°'~5 Measurements of sebum excretion rate showed no significant effect. 3°,32,33 However this may be, patients under treatment often report a gradual and progressive reduction in skin greasiness, v,32 Azelaic acid, therefore, has an effect on two and possibly three of the factors mentioned above as important in acne. It has been suggested that for hyperpigmentary disorders the prime mechanism of action might involve the reduction of cellular energy formation. Can the same apply on acne? In vitro, azelaic acid inhibits aerobic respiration ~I and anaerobic glycolysis, J2 and this could account for the in vitro and in vivo inhibition

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Fig. 1. Lentigo maligna before treatment with topical azelaic acid (original formulation6) (A). B, Same patient 10 years after cessation of treatment. of both aerobic microorganisms and the anaerobic P. acnes. The reversible inhibition of proliferation in neonatal mouse keratinocytes28 could also be due to reduction of cellular energy formation. It is thought that anaerobic glycolysis contributes most of the energy supply of the sebaceous gland, 34 and it has further been shown that the anabolic effect of dihydrosterone on the sebaceous gland of the Syrian hamster is directly correlated with its ability to stimulate anaerobic glycolysis in the cell. 35 If this is so, a possible influence of azelaic acid on sebaceous gland activity should be considered.

POSSIBLE INDICATIONS FOR AZELAIC ACID Let us now evaluate the present position concerning azelaic acid as a practical therapeutic agent. Acne. In a recent study 3° topical azelaic acid (a 20% cream) was compared with oral tetracycline (1 gm/day for 6 months) in 45 patients with different forms of acne, and both were found to be effective. International multicenter trials, reported at the Satellite Symposium on Azelaic Acid at the XV[I World Congress of Dermatology, Berlin, May 1987, have shown that topical azelaic acid is as effective as benzoyl peroxide, retinoin, and oral

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Fig. 2. Acne vulgaris before (A) and after (B) 7 months' treatment with topical azelaic acid (Schering AG, Berlin, West Germany). tetracycline and significantly better than placebo. The particular advantages of azelaic acid are: (1) it can be applied topically, and used in recurrences without giving rise to allergic or phototoxic reactions; (2) it is effective in different forms of acne (comedogenic, papulopustular, and nodulocystic); (3) possible endocrine imbalance and teratogenicity are not involved in its use; (4) it does not have the disadvantages associated with the use of antibiotics; and (5) in our experience it diminishes the tendency to scar formation. A beneficial effect may not be observed until after 4 weeks of treatment; patients should be informed to expect this and that they may have to continue the application

beyond 6 months. Time of treatment, however, may be shortened by applying the cream three to four times a day and by rubbing it in well to ensure high penetration of azelaic acid into the lesions. The general conclusion will probably be that azelaic acid has a definite future therapeutic role in the treatment of acne, either alone or in combination with other treatments. Hyperpigmentary disorders. The azelaic acid cream, applied twice a day for some months, has been shown to have a beneficial effect in the treatment of melasma, postinflammatory melanoderma, and hypermelanosis caused by physical or photochemical agents, s Multicenter trials on its

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effect on melasma, organized by Schering AG, Berlin, are in progress. Lentigo maligna. To date, 66 cases of lentigo maligna treated with topical azelaic acid have been reported in the literature. Complete clinical and histologic regression following twice-daily treatment for 6 months or more has been reported in 50 patients from a multicenter study ~6'37 and in 7 patients from another group. ~s Twenty-seven of 50 patients from the first group are at present between 5 and 10 years posttreatment. Relapses have been observed in I1 patients, but these rapidly cleared after reapplication of the cream. With the second group, the follow-up period ranged from 2 to 13 months without signs of recurrences in any of the seven patients. ~8In a recent report involving nine cases of lentigo maligna, 38 clinical improvement was observed in four, with complete clearing in one. With the remaining five no beneficial effect was observed, and two of these, one of whom had previous surgical treatment, developed lentigo maligna melanoma, one after 12 weeks' treatment with azelaic acid and the other after 23 weeks. In evaluating these studies it must be emphasized that, as is known for other topically applied drugs, the formulation used can be of utmost importance for the clinical results. Also in the case of azelaic acid it has been demonstrated that the type of formulation can significantly affect the diffusion of the diacid through artificial membranes or nude rat skin in vitro, as well as the penetration into human skin. 39 Since in the clinical investigations different creams, and in the latter studya8 also a variety of creams and ointments, have been used, it is likely that, at least partially, differences in formulation account for the variability in therapeutic response. Lentigo maligna can progress to lentigo maligna melanoma, and before instituting any form of treatment the initial presence of this development should be diagnosed. It is possible that the two cases reported by McLean and Peter 38 of invasive melanoma appearing in lentigo maligna treated by azelaic acid for 12 and 23 weeks had malignant foci from the outset. In our series, 3 cases initially shown by electron microscopy to have abnormal melanocytes in the dermis were completely cured and are, at present, 5, 7, and 9 years posttreatment.

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In this context one must consider the fact that some clones of abnormal cells m a y be less responsive than others to the application of any cytotoxic drug. In fact, it has been shown that different strains of human malignant melanocytes in culture are affected to different extents by azelaic acid.23 This could well be mirrored in vivo. Considering the present overall results, it seems reasonable to conclude that topical azelaic acid may have a significant role in the treatment of lentigo maligna. Patients for treatment must be selected carefully, however, with informed consent and, in our opinion, azelaic acid should be seriously considered for early cases and for patients for whom, because of old age or the extent and site of the lesion, surgical or other treatments are not a practical possibility. Lentigo maligna is a relapsing condition, whatever the form of treatment, and clearly, with recurrences, reapplication of topical treatment is easier and preferable to, for instance, repeated surgery. In relaPSeS following initial surgery or xrray therapy, topical treatment with azelaic acid could be a method of practical choice. COMMENT Ten years' study have shown that azelaic acid, a naturally occurring and nontoxic substance, has relevant biologic properties that can be exploited in the treatment of skin disorders of different origin. Its effectiveness as a therapeutic agent ha s been clearly demonstrated in acne vulgaris. Of particular importance are its biologic activities on abnormal melanocytes that have led to the possibility of obtaining good results in the treatment of melasma and to the highly durable therapeutic responses in lentigo maligna. The necess!ty of achieving and maintaining a high intralesional concentration of the diacid for long periods is a limiting factor, and, at present, it i s possible to use it only by topical application, in this context, attention has to be drawn to the fact that formulation can significantly affect the penetration of the diacid into the skin; from a practical point of view, therefore, standardized formulations and regimen of application for the different types of skin lesions are necessary. However, the potential of azelaic acid as a drug active against malignant melanocytes

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both in vitro and in vivo has been clearly shown, and the possibility of adapting it for systemic treatment of malignant melanoma should be investigated. The mechanism of action of the diacid is still under investigation. From the correlation of laboratory results with the in vivo observations, it seems possible' to suggest that the mode of action of azelaic acid is related to its higher penetrability of abnormal cells as compared with normal cells, and to its capability of reversibly inhibiting essential enzymatic activities. This capability, according to recent studies from our laboratory,* seems strictly correlated with the presence in the molecule of two appropriately spaced negatively charged carboxylic groups. From a general biologic point of view, its properties as so far demonstrated have made azelaic acid a new and useful investigative probe for the study of a number of fundamental metabolic processes, and its value and that of other mediumchain length dicarboxylic acids in this connection are probably by no means yet exhausted. *Passi S, Nazzaro-Porro M, Picardo M, Breathnach AS. POssible mechanism of action of azelaie acid. Proceedings of Vlth European Workshop on Melanin Pigmentation, Murcia, Spain, Sept. 23-26, 1985. REFERENCES 1 . Mortensen PB. Dicarboxylic acids and the lipid metabolism. Dan Med Bull 1984;31:121-45. 2. Nazzaro-Porro M, Passi S, Picardo M, Mercantini R, Breathnach AS. Lipoxygenase activity of Pityrosporum in vitro and in vivo. J Invest Dermatol 1986;87:108-12. 3. Nazzaro-Porro M, Passi S. Identification of tyrosinase inhibitors in cultm'es of Pityrosporum. J Invest Dermatol 1978;71:205- 8. 4. Riley PA. Pathologica! disturbances of pigmentation. In: Jarrett A, ed. The physiology and pathophysiology of the skin. London: Academic Press, 1974:1175-89, (Vol. 3.) 5. Nazzaro-Porro M, Passi S. Effetto degli acidi dicarbossilici in alcune dermatosi pigmentarie. G Ital Dermatol 1978;113:401-4. 6. Nazzaro-Porro M, Passi S, Balus L, Breathnach AS, Martin B, Morpurgo G. Effect of dicarboxylic acids on lentigo maligna. J Invest Dermatol 1979;73:296-305. 7, Nazzaro-Porro M, Passi S, Picardo M, Breathnach AS, Clayton R, Zina G. Beneficial effect of 15% azelaic acid cream on aene vulgaris. Br J Dermatol 1983;109:45-8. 8. Passi S, Nazzaro-Porro M, Picardo M, Mingrone G, Fasella P. Metabolism Of straight saturated medium chain length (C9 to C:.) dicarboxylic acids. J Lipid Res 1983;34:1140-7.

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9. Breathnach AS, Nazzaro-Porro M, Passi S. Azelaic acid. Br J Dermatol 1984;11:115-20. 10. Nazzaro-Pon'o M, Passi S, Picardo M, Breathnach AS. Possible mechanism of action of azelaic acid on acne. J Invest Derrnatol 1985;84:451. 11. Passi S, Picardo M, Nazzaro-Porro M, Breathnach AS, Confaloni AM, Serlupi-Crescenzi G. Antimitochondrial effect of saturated medium chain length (C~ to Cj3) dicarboxylic acids. Biochemical Pharmacol 1984;33: 103-8. 12. Bargoni N, Tazartes O. On the effect of alifatic saturated dicarboxylic acids on anaerobic glycolysis in chicken embryo. J Biochem 1983;32:285-390. 13. King K, Leeming JP, Holland KT, Cunliffe WJ. The effect of azelaic acid on cutaneous microflora in vivo and in vitro. J Invest Dermatol 1985;84~438. 14. Leeming JP, Holland KT, Bojar RA. The in vitro antimicrobial effect of azelaic acid. Br J Dermatol 1986;115:551-6. 15. Rach P, T6pert M. Pharmacologic investigation of azelaic acid. J Invest Dermatol 1986;86:327. 16. Pehamberger H. Das maligne Melanom der Haut, Prognose und Therapie. Wien: Verlag V, 1984:46-52. 17. Robins EJ, Breathnach AS, Ward B J, e t a l . Effect of dicarboxylic acids on Harding-Passey and Claudman 891 melanoma cells in tissue culture. J Invest Dermatol 1985;85:216-21. 18. Leibl H, Stingl G, Pehamberger H, Korschan H, Konrad K, Wolff K. Inhibition of DNA synthesis of melanoma cells by azelaic acid. J Invest Dermatol 1985; 85:417-22, 19. Pathak MA, Ciganek ER, Wick M, Sober AJ, Farinelli WA, Fitzpatrick TB. An evaluation of the effectiveness of azelaie acid as a depigmenting and chemotherapeutic agent. J Invest Dermatol 1985;85:222-8. 20. Mensing H, Remier Hevia C, Schmidt KU. Chemotactic behaviour of melanoma cells in vitro: correlation with plasminogen activator activity and influence of azelaic acid. J Invest Dermatol 1985;84:445. 21. Breathnach AS, Robins EJ, Bhasin Y, Ethridge L, Nazzaro-Porro M, Passi S. Observations on cell kinetics and viability of a human melanoma cell line exposed to azelaic acid. Histol Histopathol 1986;1:235-40. 22. Hu F, Mah K, Teramura JD. Effect of dicarboxylic acids on normal and malignant melanocytes in culture. Br J Dermatol 1986;I 14:17-26. 23. Geier G, Hauschild T, Bauer R, Kreysel W. Der Einfluss yon Azelains/iure auf das Wachstum yon Melanomazellkulturen im Vergleich zu Fibmblastenkulturen. Hautarzt 1986;37:146-8. 24. Picardo M, Passi S, Sirianni MC, et al. Activity of azelaic acid on cultures of lymphoma- and leukaemia-derived cell lines, normal resting and stimulated lymphocytes, and 3T3 fibroblasts. Biochemical Pharmacol 1985;34: 1653-8. 25. Robins EJ, Breathnach AS, Bennett D, e t a l . Ultrastructural observations on the effect of azelaic acid on normal human melanocytes and a human melanoma cell line in tissue culture. Br J Dermatol 1985;113:687-97. 26. Ward BJ, Breathnach AS, Robins EJ, et al. Effect of L-carnitine on cultured murine melanoma cells exposed to azelaic acid. J Invest Dermatol 1986;86:438-41.

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27. Ward B J, Breathnach AS, Robins EJ, et al. Analytical, ultrastructural, autoradiographic, and biochemical studies on 3H-dicarboxylic acid added to cultures of melanoma cells. Br J Dermatol 1984;3:115-20. 28. Detmar M, Mtiller R, Stadler R, Offanos CE. Dicarboxylic acids modulate protein synthesis and inhibit proliferation of keratinoeytes in vitro. J Invest Dermatol 1986;87:136. 29. Nazzaro-Porro M, Passi S, Zina G, et al. Effect of azelaic acid on human malignant melanoma. Lancet 1980; 2:1109-11. 30. Bladon PT, Burke BM, Cunliffe WJ, Forster RA, Holland KT, King K. Topical azelaic acid and the treatment of acne: a clinica! and laboratory comparison with Oral tetracycline. Br J Dermatol 1986;114:493-9. 31. Wilkie D. Anti-mitochondrial drugs in cancer chemotherapy: preliminary communication. J R Soc Med 1979; 72:599. 32. Marsden JR, Schuster S. The effect of azelaic acid on acne. [letter]. Br J Dermatol 1983;109:723. 33. Gassmueller H, Graupe K, Orfanos CE. Azelaic acid and sebum excretion rate [letter]. Br J Dermatol 1985; 113:800-2.

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34. Freinkel RK. Metabolism of glucose C- 14 by human skin in vitro. J Invest Dermatol 1960;34:37-42. 35. Adachi K, Takayasu S. The mechanism of testosterone action on the sebaceous glands of the syrian hamster. Montagna W, Stoughton RB, Van Scott EJ, eds. Advances in biology of skin. Vol. 12: Pharmacology and the skin. New York: Appleton-Century, 1972:381-401. 36. Nazzaro-Porro M, Passi S, Zina G, Breathnach AS. Five years observations on the effect of azelaic acid on lentigo maligna. J Invest Dermatol 1982;78:331. 37. Nazzaro-Porro M, Passi S, Breathnach SA, Zina G. 10 years observations on the effect of azelaic acid on lentigo maligna. J Invest Demaatol 1986;87:438. 38. McLean I3I, Peter KK. Apparent progression of lentigo maligna to invasive melanoma during treatment with topical azelaic acid. Br J Dermatol 1986;114:685-9. 39. Maru U, Michaud P, Garrigue J, Oustrin J, Rouffiae R. Diffusion in vitro e t p6n6tration cutan6e de pr6parations d'acide az61aique: recherche de eorrelaticns. J Pharm Belg 1982;37:207-13.

ABSTRACTS

Anti-keratin antibodies Hintner H: Hautarzt 1987;131-7 (German) IgG antikeratin-filament autoantibodies occur in all human sera and reach high liters in the sera of patients with various cutaneous and noneutaneous diseases. At indirect immunofluorescence, these autoantibodies may, depending on their titer, appear as "upper cytoplasmic" antibodies or "stratum corneum" antibodies. In vitro, IgG antikeratin-filament antibodies significantly enhance (as opsonins) the phagocytosis of keratin-filament aggregates by human monocytes and polymorphonuclear leukoeytes. They may therefore, also in vivo, play a role in the removal of insoluble extracellular keratin-filament aggregates generated by necrotic or apoptotic cell death. Keratin (Civatte) bodies and deposits of localized cutaneous amyloid are examples Of such keratin-filament autoantibodies, which may, at indirect immunofluorescence, appear as "general cytoplasmic" antibodies that also occur in human sera but do reach high tilers in the sera of patients with various diseases. The regular presence of lgM in keratin bodies or deposits of localized cutaneous amyloid therefore probably represents the binding of lgM antikeratin-filament autoantibodies to their respective antigens. To what extent these in vivobound autoantibodies prevent any further damaging reaction by the immune system in response to the liberation of keratin-lilament autoantigen is as yet unclear. Yehudi M, Fehnan, M.D.

The Stewart-Treves syndrome: a hemangiosarcoma in

chronic lymphedema. UItrastructural analysis at various stages of clinical development Marseh WC: Hautarzt 1987;38:82-7 (German) Ultrastructural studies of angiosarcoma in chronic lymphedema (Stewart-Treves syndrome) at various stages of development show

that endothelial cell proliferation originates not in the lymphatic but in the blood capillary vessels. The results indicate that the term lymphangiosarcoma is no longer suitable to describe the histopathologic characteristics of Stewart-Treves syndrome. Yehudi M. Felman, M.D.

Oral acyclovir prophylaxis of herpes simplex infections after bone marrow transplantation: clinical and clinical. pharmacological study Ehninger G, Vallbracht A, Schuch K, et al: Klin Wochenschr 1986;64:570-4 (German) Viral infections are one of the major complications after bone marrow transplantation, with high mortality and morbidity, Forty-six patients between 3 and 48 years old (median, 15 years) received orally 400 mg (under age 6, 200 rag) acyclovir four times daily from day 12 before to day 84 after bone marrow transplantation. They were concomitantly treated with anti-cytomegatovimshyperimmunoglobulin and cotrimoxazote. During acyclovir prophylaxis seven patients had herpes simplex vires infections; all of them were serepositive before bone marrow transplantation. No acyclovir was present in the plasma of five of six patients with herpes simplex virus infections. Three of them had noncompliance, and a lack of acyclovirabsorption developed in two patients. No drug-related Side effects were observed. Laboratory tests did not show liver or renal toxicity. Oral acyelovir reduced the incidence of herpes simplex infections after bone marrow transplantation. Herpes infections occurred only in patients with noncompliance or lack of aeyclovir absorption, Yehudi M. Felman, M.D.